Sealing devices are used in car water pumps for preventing water leakage (see Patent Literature 1). A sealing device according to a conventional example will be described with reference to FIG. 7. FIG. 7 is a schematic cross-sectional view of the sealing device according to the conventional example. The illustrated sealing device 700 serves the function of sealing an annular gap between a shaft hole provided in a housing (not shown) and a rotating shaft (not shown) inserted through this shaft hole.
In the sealing device 700 according to this conventional example, a resin sealing member 720 and an elastic sealing member 730 made of rubber or the like are fixed to a cartridge case 710 so that they can be handled as one component. The cartridge case 710 includes a cylindrical case main body 711 fitted to an inner circumferential surface of the shaft hole, an outward flange 712 extending radially outward from one end portion of the case main body 711 on a sealed fluid side, and an inward flange 713 extending radially inward from an end portion of the case main body 711 opposite from the sealed fluid side. The resin sealing member 720 is firmly secured by being held in between a pair of first and second metal supporting members 740 and 750 that are fixedly fitted to each other. The elastic sealing member 730 includes an outer peripheral sealing portion 731 that seals an annular gap between the outer circumferential surface of the second supporting member 750 and the inner circumferential surface of the case main body 711, and a sealing lip portion 732 slidable on the outer circumferential surface of the rotating shaft.
With the resin sealing member 720 fixed by the first supporting member 740 and second supporting member 750, and the elastic sealing member 730 being mounted on the inner circumferential side of the case main body 711, an adapter 760 is press-fitted. Accordingly, the resin sealing member 720 and elastic sealing member 730 are fixedly set in position in the axial direction. The distal end of the inward flange 713 is press-joined so that the resin sealing member 720 and elastic sealing member 730 are fixedly set in position in the radial direction (see press-joined portion 714 in the drawing).
The adapter 760 is press-fitted, as mentioned above. Generally, it is difficult to achieve precise positioning of press-fitted members because of the high sliding resistance during the press-fitting. In the case with the sealing device 700 according to the conventional example shown in FIG. 7, however, the resin sealing member 720 is firmly secured by the first supporting member 740 and second supporting member 750, and the outer circumferential side of the second supporting member 750 is elastically pressed by the outer peripheral sealing portion 731 of the elastic sealing member 730. The resin sealing member 720 is therefore maintained in a stable attitude. Accordingly, the resin sealing member 720 fully exhibits its function. The sealing function on the outer circumferential side is also fully exhibited, since the annular gap between the outer circumferential surface of the second supporting member 750 and the inner circumferential surface of the case main body 711 is sealed by the outer peripheral sealing portion 731 of the elastic sealing member 730.
As described, the illustrated sealing device 700 fully exhibits its function as a sealing device even if the positioning precision of the adapter 760 is low. The shortcoming of this sealing device 700, however, is that the number of parts is large as it requires several components. Generally, with an increase in the number of parts, not only the cost increases, but also measurement errors tend to be large, so that stricter dimension control is necessary. Another shortcoming is that it is difficult to reduce the radial size because of the configuration in which the annular gap between the outer circumferential surface of the second supporting member 750 and the inner circumferential surface of the case main body 711 is sealed by the outer peripheral sealing portion 731 of the elastic sealing member 730. It may therefore be impractical to adopt the configuration of the above-described sealing device 700 if the annular gap between the housing and the shaft is small.